Microelectromechanical systems (MEMS) technology provides a way to make very small mechanical structures and integrate these structures with electrical devices on a single substrate using conventional batch semiconductor processing techniques. One common application of MEMS is the design and manufacture of sensor devices. MEMS sensors are widely used in applications such as automotive, inertial guidance systems, household appliances, game devices, protection systems for a variety of devices, and many other industrial, scientific, and engineering systems.
One example of a MEMS inertial sensor is a MEMS accelerometer. MEMS accelerometers are sensitive to acceleration and may be configured to sense acceleration forces along one, two, or three axes or directions. One common form of MEMS accelerometer uses one or more movable structures that move under acceleration above a substrate. The movement of the movable structure changes capacitance, and an electrical circuit connected to the MEMS accelerometer structure measures the change in capacitance to determine the acceleration forces.
In order to sense motion along multiple axes, MEMS accelerometers may include multiple movable structures that move independently of one another in response to accelerations. As these devices continue to shrink in size, it becomes desirable to reduce the collective size of these movable structures. But reducing the collective size of the movable structures can make it increasingly difficult to meet predetermined sensitivity, linearity, and reliability requirements. In addition, due to smaller sizes and travel distances of the movable structures, some MEMS accelerometers may have insufficient restoring force and can therefore be vulnerable to damage from high impact loads.